The present invention relates to a temperature compensation circuit that varies its output in accordance with a temperature change, a trimming circuit using such a temperature compensation circuit, and an acceleration detector using such a trimming circuit.
Temperature compensation circuits are nowadays used to compensate for variations caused by a temperature change so as to maintain a constant output (for example, refer to International Publication No. WO 2005/086343). The temperature compensation circuit described in International Publication No. WO 2005/086343 is incorporated in a series regulator. The temperature compensation circuit includes a regulator circuit and a resistor coupling, which is formed by at least two resistor elements. The resistor coupling adjusts a temperature coefficient gradient to compensate for voltage variations caused by a temperature change.
Another type of temperature compensation circuit adjusts the temperature gradient. This circuit includes, between a power supply voltage line and a ground voltage line, a line of first and second resistor means, which are connected in series, and a line of third and fourth resistor means, which are connected in series. In this temperature compensation circuit, the first and fourth resistor means are each formed by two resistor elements having negative temperature coefficients, and the second and third resistor means are each formed by a resistor element having a negative temperature coefficient and a resistor element having a positive temperature coefficient. Further, a plurality of series-connected resistor elements are connected between a first connection node of the first and second resistor means and a second connection node of the third and fourth resistor means. An output is retrieved from the line connecting the first and second connection nodes.
Depending on the application, a temperature compensation circuit having a wide applicable temperature range may be required. For example, the temperature compensation circuit may be employed in an acceleration detector, which is used in locations where the temperature changes greatly. However, the conventional temperature compensation circuit has a narrow applicable temperature range. Thus, when the conventional temperature compensation circuit is applied for a wide temperature range, the linearity becomes poor. This is because the resistance of the resistor elements in the temperature compensation circuit does not vary in the manner of a first order function as the temperature changes. Rather, the resistance actually varies along a curve based on a second order or third order function. When the applied temperature range is narrow, the influence of high order functions is small enough to be ignorable. Thus, the conventional temperature compensation circuit can be used. However, when the applied temperature range is widened, the influence of high order functions becomes significant.